You should probably take your foot off the gas if you see a white bicycle sitting alone, without a rider outside your window.
The white bicycles are known as "ghost bikes," and they represent a tragedy that happened along the road.
How Did Ghost Bikes Start?
According to
GhostBikes.org, the first somber memorials involving white bikes popped up in St. Louis in 2003.
The Ghost Bike is placed near the crash site where a bicyclist was killed or hit on the street. The bike is typically locked to a street sign and accompanied with a sign that explains the significance of the memorial.